All Derfs are Enajs. One-third of all Enajs are Derfs. Half of all Sivads are Enajs. One Sivad is a Derf. Eight Sivads are Enajs. The number of Enajs is 90. How many Enajs are neither Derfs nor Sivads?

The earth has a belt around the equator that is perfectly fit. If a
measurement of 1 foot is added to the belt, theoretically the belt will
no longer touch the earth at any point. What is the new distance between
the surface of the earth and the belt?

When a man is 3/8 of the way across a railroad bridge that goes from
point A to point B, he hears a train approaching at 60 mph. If he runs
back he will meet the train at A, and if he runs forward the train will
overtake him at B. How fast can the man run?